Itsuka Shido is a high school boy. On the last day of the spring holidays, an explosion destroys the town and a girl in armor appears in front of him. Shido's step-sister, Kotori, tells him that the girl is called "Special Disasterous Designated Creature: Spirit", which causes a timespace quake. Kotori disclosed that she is the commander of the anti-spirit organization Ratatosk and orders him to go out on a date with the spirit girl. Kotori says, "I don't ask you to beat the spirit. Just let her fall in love with you and save the world."